Daytime lethargy has definitely gone down. I had to visit the sleep nurse after a week last Friday to return the oxygen sensor (they only have one or two sensors to give out with the test CPAPs - I get to buy my own CPAP next month) and she said my oxygen levels were already back to normal without any need to further adjust the pressures. First week or so involved a lot of waking up at night, but now I barely notice the thing!